The present invention relates to a scroll type fluid machine and, more particularly, to a structure of a thrust bearing of a scroll type fluid machine.
Fundamental components of a scroll type compressor, which is a typical example of a fluid machine, are shown in FIG. 1, in which a reference numeral 1 depicts a stationary scroll, 2 an orbiting scroll, 3 a discharge port, 4 compression chambers, 0 a fixed point on the orbiting scroll, and 0' a fixed point on the orbiting scroll. The stationary scroll 1 and the orbiting scroll 2 are constituted by wraps having the same convolutions and formed of a combination of involutes of arcs or the like, as is well known.
In operation, the orbiting scroll 2 is assembled with the stationary scroll 1 as shown in FIG. 1. The stationary scroll 1 is moved in an orbiting motion without changing its angular attitude, i.e., it orbits through angles 0.degree., 90.degree., 180.degree. and 270.degree. as shown in the figure. With the orbital movement of the orbiting scroll 2, the volumes of crescent shaped compression chambers 4 formed between the wraps of the stationary scroll 1 and the orbiting scroll 2 are reduced sequentially to take in and compress fluid. The compressed fluid is moved towards the center and discharged through the discharge port 3. During this operation, the distance between the fixed points 0 and 0' is held constant, which distance is expressed by 00'=p/2-t, where p and t are the gap length between the wraps and the thickness of the wraps, respectively. In this case, p corresponds t the pitch of the wraps.
Next, the detailed construction of such a scroll type compressor and its operation will be described.
FIG. 2 shows an example of such a scroll type compressor which may be used in a refrigerator or air conditioner and which is of the so-called semi-sealed type. In FIG. 2, reference numeral 1 is a stationary scroll, 2 an orbiting scroll assembled with the stationary scroll 1, 3 a discharge port, 4 compression chambers, 55 a shaft of the orbiting scroll, 6 a crankshaft having an eccentric hole 42 in which the orbiting scroll shaft 55 is fitted to orbit the orbiting scroll 2, 7 a bearing support for the orbiting scroll 2, 8 the rotor of an electric motor, 9 the stator thereof, 10 a first balancer, 11 a second balancer, 12 a key I for fixedly securing the first balancer 10 to the crankshaft 6, 13 a spacer, 14 a key II for fixedly securing the rotor 8 to the crankshaft 6, 15 a washer I, 16 an anti-rotation washer, 17 a rotor fixing nut, 18 a stirrer, 19 bolts I for securing the second balancer 11 to an end ring 75 of the rotor 8, 20 a discharge chamber connected to the discharge port 3, 21 bolts II for securing the discharge chamber 20, the stationary scroll 1, the orbiting scroll 2 and the bearing 7 to a shell 23, 22 an O ring, 24 bolts for securing the stator, 25 a washer II, 26 a support ring, 27 a bottom plate, 28 a hole formed in the bottom plate 27, 29 to 32 blind screw holes I, II, III and IV, 33 an oil hole, 34 an Oldhams coupling for preventing the orbiting scroll 2 from rotating about its axis, 35 a thrust bearing assembled in the bearing 7, 36 a metal bearing sleeve I for reducing friction between the eccentric hole 42 and the orbiting scroll shaft 55, 37 a metal bearing sleeve II for reducing friction between the crankshaft 6 and the bearing 7, 38 a thrust receiver for receiving thrust on a stepped portion of the crankshaft 6, 39 a metal bearing sleeve III for reducing friction between an end portion of the crankshaft 6 and the bottom plate 27, 40 a hermetic terminal I, 41 a hermetic terminal II, and 42 an eccentric hole of the crankshaft.
FIG. 3 is a cross section taken along a line III--III in FIG. 2, in which reference numeral 43 indicates Oldhams guide grooves which receive projection 59 of the Oldhams coupling (see FIG. 9), 44 an intake port, 45 an O ring groove I, 46 bolt holes I, and 47 a female screw I. In FIG. 4, which is a cross section taken along a line IV--IV in FIG. 2, reference numeral 48 indicates a communicating portion.
Various components of the scroll type compressor constructed as above will be described in more detail.
FIGS. 5a and 5b show the stationary scroll 1 having the discharge port 3, in which reference numeral 49 is the stationary scroll wrap, 50 a base plate forming a base of the stationary scroll 1, 51 a through-hole II for bolts, and 52 spot facings for bolts for securing the stationary scroll 1. The stationary scroll 1 has the form of a thick disk having a convoluted groove cut therein forming the wrap 49.
The discharge port 3, formed in a central portion of the base plate 50, has a thread cut in its inner surface. The spot facings 52 are formed so that, when the discharge chamber 20 is assembled therewith, head portions of the assembling bolts do not protrude from the mating surface.
FIG. 6 shows the orbiting scroll 2, in which reference numeral 53 depicts the wrap, 54 a base plate, 55 the orbiting scroll shaft, and 56 projections for the Oldhams coupling. The orbiting scroll wrap 53 is formed integrally with the base plate 54, as are the projections 56 and the scroll shaft 55.
FIG. 7 shows a rear view of the orbiting scroll 2, in which reference numeral 57 depicts a balancer fixed thereto by bolts 58. The center of the scroll shaft 55 coincides with the center of the base plate 54. The projections 56, having lengthwise axes passing through the center of the base plate, are engaged with the Oldhams coupling 34 to restrict the rotation of the orbiting scroll 2 about its axis. The orbiting scroll shaft 55 is fitted in the eccentric hole 42 of the crankshaft 6 shown in FIG. 2 and is driven by a rotational force transmitted from the rotor 8 through the crankshaft 6 to realize eccentric orbiting movement of the orbiting scroll 2. The balancer 57 functions to compensate for static unbalance due to the fact that the center of gravity of the warp 53 of the orbiting scroll 2 does not coincide with the center of the base plate 54 and hence the orbiting scroll shaft 55. With this balancer, the center of gravity of the orbiting scroll 2 is made coincident with the center of the orbiting scroll shaft 55.
FIG. 8 shows the main bearing support 7. The crankshaft 6 (FIG. 2) is fitted in the metal bearing sleeve II 37 of the bearing support 7 so that the stepped portion of the crankshaft 6 rides on the thrust receiver 38. The thrust bearing 35 supports the rear side of the orbiting scroll base plate 54 against thrust transmitted from the orbiting scroll 2. In some cases, it functions to provide a supporting force equal to or larger than the thrust of the orbiting scroll 2 by introducing an oil pressure on the surface of the thrust bearing 35. The Oldhams guide grooves 43 receive the projections of the Oldhams coupling 34 in such a manner that the projections can reciprocate in the grooves. Four intake ports 44 are provided in this example which penetrate the bearing support 7. The O ring groove 45 formed in an end face of the bearing support 7 performs sealing. Threaded screw holes 47 for assembling the bearing support 7 and the stationary scroll 1 integrally and a through-hole for the bolts for assembling the compressor are also provided. The oil hole 33 and the blind screw hole IV 32 are also formed therein. The blind screw hole 32 can be used to attach a gauge to measure the pressure of the lubricating oil. An end face of the bearing support 7 in which the through-holes 46 and the threaded screw holes I 47 are formed is higher than the end face of the thrust bearing 35 by a distance corresponding to the sum of the thickness of the orbiting scroll base plate 54 and a distance in a range from 10 to 50 microns so that, when the stationary scroll 1 is fixed to the end face of the bearing support 7, the orbiting scroll 2 can orbit, as clearly shown in FIG. 2.
In FIG. 9, which shows the Oldhams coupling 34, reference numeral 60 depicts guide grooves for receiving the projections 56 of the orbiting scroll 2, and 61 an annular ring.
The Oldhams coupling 34 functions to prevent the orbiting scroll 2 from rotating about its axis and defines, together with the crankshaft 6, the orbit of the orbitins scroll 2. The projections 59 of the Oldhams coupling 34 fit in respective ones of the Oldhams guide grooves 43 of the bearing support 7. A line connecting the projections 59 passes through the center of the ring 61 and forms a right angle to a line connecting the grooves at the center.
When the orbiting scroll 2 moves eccentrically upon rotation of the crankshaft 6, the projections 59 of the Oldhams coupling 34 reciprocate in the Oldhams guide grooves 43 of the bearing support 7, and thus the Oldhams coupling 34 itself reciprocates. Under this condition, the orbiting scroll 2 engaged with the grooves 60 reciprocates relatively with respect to the Oldhams coupling 34. As a result, the orbiting scroll 2 orbits along a composite of the orthogonal reciprocating paths.
In FIG. 10, which shows the crankshaft 6, reference numeral 62 depicts an oil groove I, 63 an oil groove II, 64 a key groove I, 65 a key groove II, 66 a fitting portion of the crankshaft, 67 a rotor mounting portion, 68 a shaft fitting portion, 69 a rotor mounting nut screws, and 70 an anti-rotation washer groove.
The crankshaft 6 is driven by the driving force of the rotor 8 mounted on the rotor mounting portion 67. It in turn drives the orbiting scroll 2 fitted in the eccentric hole 42 in which the metal bearing sleeve I 36 is provided. The metal bearing sleeve I 36 may be made of a known bearing metal alloy. Alternatively, it may be replaced by so-called needle bearing. The metal bearing sleeve 36 is provided at the side opposite to a load side with the oil groove II 63. The shaft fitting portion 66 fits in the metal bearing sleeve II 37 of the bearing support 7, and the stepped portion of the crankshaft 6 is supported by the thrust receiver 38 of the bearing support 7. The oil groove I 62 is also formed in the shaft fitting portion 66 to form an oil supply system. A pair of the oil holes 33 communicate the oil groove I 62 with the oil groove II 63. One of the oil holes 33 penetrates the center of the crankshaft 6 to supply oil to the shaft fitting portion 68. The key groove I 64 is used to secure the first balancer (FIG. 2), and the key groove II 65 is used to mount the rotor 8. The shaft fitting portion 68 is fitted in the metal bearing sleeve II 37 of the base plate 27 (FIG. 2) to restrict radial movement of the crankshaft 6. The rotor mounting screw 69 is engaged with the nut 17 with a projecting portion of the washer 16 being fitted in the washer groove 70.
In FIG. 11, which shows the first balancer 10, reference numeral 71 depicts a balance weight, 72 a cylinder portion, 73 a fixed portion, and 74 a key groove III.
The first balancer 10, together with the second balancer 11, functions to balance the assembly against a centrifugal force arising due to the eccentric orbital movement of the orbiting scroll 2, to thereby assure quiet and smooth running of the rotary system of the machine. The first balancer 10 is fixedly secured to the key groove I 64 of the crankshaft 6 by the key I 12 inserted into the key groove III 74 provided in the fixed portion 73. The balance weight 71 is provided through the cylinder portion 72 in a space formed between the bearing support 7 and the stator 9 so as to minimize the size of the compressor. The mass of the balance weight 71 is minimized by arranging it as close to the shaft of the orbiting scroll 2 as possible and as remote from the center of the crankshaft 6 as possible. If the orbiting scroll 2 is made of cast iron or cast iron containing graphite particles, its weight becomes substantial, and thus it is necessary to make the balance weight heavy correspondingly. However, with the described structure of the compressor, the radial size of the compressor can nevertheless still be minimized.
FIG. 12 shows the rotor 8 of the electric motor. In FIG. 12, reference numeral 75 is an end ring and 76 a key groove IV. The rotor 8 is fixedly mounted to the key groove II 65 of the crankshaft 6 by the key II 14 fitted in the key groove IV 76. The second balancer 11 is provided at one end of the end ring 75 to balance the orbiting scroll 2 and, together with the first balancer 10, minimize the amount of vibration of the machine.
In FIG. 13a, which shows a lower side view of the rotor 8, reference numeral 77 depicts screw holes for mounting the stirrer 18. The second balancer 11 is secured to the end ring 75 by the bolts I 19.
The various components described individually are assembled as shown in FIG. 14. In FIG. 14, the crankshaft 6 is fitted in the bearing 7, and then the Oldhams coupling 34 is inserted into the bearing support 7. Thereafter, the orbiting scroll 2 is fitted through the Oldhams coupling 34 to the crankshaft 6, and then the stationary scroll 1 is secured by the bolts II 78 to the bearing support 7. Following this, the first balancer 10 is mounted to the lower side of the crankshaft 6. The radial position of the rotor 8 is regulated by the spacer 13 with respect to the crankshaft 6. Then, the washers 15 and 16 are inserted into a lower portion of the rotor 8, and the first balancer 10, the spacer 13, and the rotor 8 are assembled and secured to the crankshaft 6 by the nuts 17. As will be clear from FIG. 2, the first balancer 10 abuts against the stepped portion of the crankshaft 6 and serves as a stop. Finally, the second balancer 11 and the stirrer 18 are mounted on the rotor 8 to complete the scroll-rotor assembly.
FIG. 15 illustrates the assembly of the compressor. The discharge chamber 20, having the O ring 22, is secured to the upper end of the scroll-rotor assembly by screwing the bolts III 79 through the stationary scroll 1 into threaded screw holes II 80 formed in the upper surface of the shell 23, to which the stator 9 is secured by the bolts 24. The inner surface of the upper end portion of the shell 23 has formed therein an O ring groove 81 in which the O ring I 22 is received. Reference numeral 82 in FIG. 2 indicates the coil end of the stator 9. As is clear from FIG. 2, a spline is formed in the rear of lower surface of the bearing support 7, which is fitted in the shell 23, for providing a precisely annular air gap between the rotor 8 and the stator 9 of the electric motor.
Hermetically sealed terminals 40 and 41 are mounted on the outer periphery of the shell 23. The hermetic terminal 40, which may be, for example, of a two-pin type, is connected to a winding protection circuit of the stator 9, and the hermetic terminal 41, which may be of a three-pin type, is used to feed three-phase a.c. current to the stator winding. The terminals are insulated from the shell 23.
FIG. 16 depicts the assembly of the bottom plate 27 to the shell 23. In FIG. 16, the metal bearing sleeve 39 of the bearing 88 of the bottom plate 27 is fitted on the shaft fitting portion 68 of the crankshaft 6. A spline 87 facilitates the coaxial arrangement thereof. The bottom plate 27 is secured to the shell 23 by means of threaded screw holes III 85 in a shell flange 84 and bolts IV 89. The screw hole 28 is formed in the bottom plate 27 for fluid intake. The structure shown in FIG. 2 is thus completed.
The operation of the scroll type compressor shown in FIG. 2 will now be summarized.
When three-phase a.c. current is supplied through the terminal 41 to the stator 9, torque is produced in the rotor 8 by which the crankshaft 6 is rotated. The rotary motion of the crankshaft 6 is transmitted through the orbiting scroll shaft 55 fitted in the eccentric hole 42 of the crankshaft to the orbiting scroll 2, and the latter orbits with the aid of the Oldhams coupling 34 mounted on the bearing support 7, resulting in a compression operation as shown in FIG. 1 Gas, such as Freon, is sucked through hole 28 in the bottom plate 27, the air gap between the rotor 8 and the stator 9, and a gap between the stator 9 and the shell 23 to the intake port 44 (FIG. 3) of the bearing support 7. This gas then flows through the communication passage 48 to the compression chamber 4 between the orbiting scroll 2 and the stationary scroll 1.
A lubricating oil supply system for the unit includes an oil separator (not shown) which may be housed in the discharge chamber 20. Oil separated by the separator flows through the oil hole 33 formed in the stationary scroll 1 and the oil hole 33 formed in the bearing support 7 to the metal bearing sleeve II 37, and then through the oil hole 33 seen in FIG. 10 and the oil grooves I 62 and II 63 to the thrust bearing 35, the metal bearing sleeve III 39 and the thrust receiver 38. A portion of the oil from the thrust bearing 35, together with the gas, is taken into the compression chamber. Oil flowing from the thrust receiver 38 and the metal bearing sleeve III 39 flows into the interior of the shell 23 and is atomized at a rate depending upon the flow rate of the gas and the action of the stirrer 18. The atomized oil, together with the gas, is taken into the compression chamber. Oil in the compression chamber 4 fills radial and axial gaps between the wrap 49 of the stationary scroll 1 (FIG. 5a) and the wrap 53 of the orbiting scroll 2 to thus minimize the leakage of the gas. Oil from the thrust bearing 35 lubricates the respective sliding surfaces of the members of the Oldhams coupling 34. Oil entering the discharge chamber 20 in this manner is separated again by the separator and forced to the oil supply line by the pressure of the discharging gas. On the other hand, oil which is not separated out by the oil separator circulates through the compressor with the refrigerant (when the compressor is used as in a refrigerator or air conditioner) and is returned to the hole 28 together with the gas. It is also possible to provide an oil separator outside the discharge chamber 20.
A protection circuit connected through the terminal 40 to the stator winding detects any overload of the stator 9 or an abnormal increase of temperature to cut off the three-phase a.c. source feeding the stator winding.
As mentioned previously, the stirrer 18 shown in FIG. 13b is secured to the end ring 75 of the rotor 8 and serves as a centrifugal fan for stirring and splashing lubricant oil, which would otherwise tend to stay in the bottom of the shell 23, to reuse it together with flowing gas. The stirrer 18 may take the form of a centrifugal fan having flat fins and can be manufactured by a simple pressing operation.
In the conventional scroll type compressor, it is usual to form the oil grooves in the surface of the thrust bearing support 7 as shown in FIG. 8. In such a case, however, an oil membrane formed between the rear surface of the orbiting scroll 2 and the flat surface of the thrust bearing support 7 cannot have the desired wedge shape, and thus the load capacity of the compressor is relatively small. Further, if the orbiting scroll 2 is deformed by a thrust force, the flat thrust bearing support 7 cannot follow such deformation, causing the load to be received by the inner periphery of the thrust bearing support 7.
Moreover, in the conventional scroll type fluid machine described above, if the thrust load applied by the orbiting scroll 2 becomes excessive, only a very small lubricating oil membrane will be produced between the rear surface of the orbiting scroll 2 and the thrust bearing support 7, resulting in consumption of the oil. This occurs because the thrust bearing is flat. Further, if the orbiting scroll 2 is deformed by a thrust force, the bearing support 7 cannot follow such deformation, and hence the thrust load is received by only a portion of the thrust bearing support 7. In any case, in the conventional structure, an oil reservoir for reserving lubricant oil must be provided peripherally of the thrust bearing support 7, causing the structure to be very complicated.